Machine type communication (MTC) applications required low-cost devices and improved coverage other than the current cellular communication system. Other narrow band (NB) devices also require coverage enhancement in a wireless network. The rapid growth in the latest development of the internet of things (IoT) also has requirements enhanced coverage mode. Repetition is one common solution to achieve coverage enhancement for most physical channels/signals. These machine-to-Machine (M2M) applications required low-cost devices and improved coverage other than the current cellular communication system. For example, some smart metering deceives are often installed in the basements of residential buildings or locations shielded by foil-backed insulation, metalized windows, or traditional thick-walled building construction. These smart devices suffer a significantly larger path-loss, such as 20 dB path loss, than that in the typical operation condition of normal devices.
More resources/power is needed to support these UEs in the extreme coverage scenario. How to obtain a response message after a contention based access transmission under a coverage gap is still an open issue. Following the current design, the resource overhead is quite large if a response message is transmitted with the corresponding control information under repeated transmission since repetition has been identified as a common technique to bridge the additional penetration losses than normal LTE devices. Further, serious resource waste can be expected because response messages as a common message are targeted for different type of UEs within a cell. It requires transmitting repeatedly to bridge a largest coverage gap.
Improvement and enhancement are required to efficiently sending and receiving contentions based response messages.